using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Web.Mvc;

namespace Kreta.Web.Helpers.Extension
{
    public static class DataSetExtensions
    {
        public static List<SelectListItem> CreateMvcGroupedSelectListItem(this DataSet ds, string keyColumn, string valueColumn, string groupNamesColumn, string groupOrderColumn = null)
        {
            DataTable dt = ds.Tables.Count > 0 ? ds.Tables[0] : null;
            if (dt == null)
            {
                return new List<SelectListItem>();
            }
            EnumerableRowCollection<DataRow> dataRowList = dt.AsEnumerable();
            if (!string.IsNullOrWhiteSpace(groupOrderColumn))
            {
                dataRowList = dataRowList.OrderBy(x => x.Field<int>(groupOrderColumn));
            }
            var groups = dataRowList
                .GroupBy(x => x.Field<string>(groupNamesColumn))
                .Select(group => new KeyValuePair<string, SelectListGroup>(group.Key, new SelectListGroup { Name = group.Key }))
                .ToDictionary(item => item.Key, item => item.Value);

            var result = dt.Rows
                .Cast<DataRow>()
                .Select(item => new SelectListItem
                {
                    Group = groups[item.Field<string>(groupNamesColumn)],
                    Text = item.Field<string>(valueColumn),
                    Value = item.Field<int>(keyColumn).ToString()
                })
                .ToList();
            return result;
        }

        public static List<SelectListItem> CreateMvcSelectListItem(this DataSet ds, string keyColumn, string valueColumn)
        {
            DataTable dt = ds.Tables.Count > 0 ? ds.Tables[0] : null;
            if (dt == null)
            {
                return new List<SelectListItem>();
            }
            EnumerableRowCollection<DataRow> dataRowList = dt.AsEnumerable();

            var result = dt.Rows
                .Cast<DataRow>()
                .Select(item => new SelectListItem
                {
                    Text = item.Field<string>(valueColumn),
                    Value = item.Field<int>(keyColumn).ToString()
                })
                .ToList();
            return result;
        }
    }
}